Lift truck



Nov. 20, 1945. w. sTUEBlNG, JR

LIFT TRUCK 2 sheets-sheet i Filed July 26, 1945 '22A/@wwe h//LL/AMrafa/ale, de 5y #5&7

Arrow/5K5' Nov. 20, 1945. w. sTuEBlNG, JR

LIFT TRUCK Filed July 26, 1945 2 Sheets-Sheet 2 Patented Nov. 20, 1945LIFT TRUCK William Stuebing, Jr., Cincinnati, Ohio Application July 26,1943, Serial No. 496,142

(c1. zar- 2) 7 Claims.

This invention relates to lift trucks, and more particularly to lifttrucks which are provided with swinging steering handles where theoperator walks and steers the truck.

An object of this invention is to provide a mechanism of an improvedcharacter for lifting and conveying articles such, for example, asmovable platforms of the type where" a quantity of material is piled onthe platform and then the loaded platform is moved from one location toanother. A further object is to provide an enicient and dependable meansfor lifting a load. A still further object is to provide for the rapidand dependable lifting of the load so that the load may be moved in aknown manner to a new location. A further object is to provide apparatusof the above character which is light in weight, sturdy in constructionand inexpensive to manufacture and operate. A further object is toprovide mechanism of the above character which may be operated with easeand with utmost safety. These and other objects will be in part obvious,and in part pointed out below.

The invention accordingly consists in the features of construction,`combinations of elements, and arrangements'of parts as will beexemplied in the structure to be hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

In the drawings, in which is shown one of many possible embodiments ofthis invention:

Figure 1 is a side elevation of the front portion of a lift truck; Y

Figure 2 is a front view of Figure l;

Figure 3 is a plan view of Figure 1 with parts broken away to expose thecentral gearing mechanism;

Figure 4 is a sectional view on the line 4-4 of Figure 3; and

Figure 5 is a wiring diagram of the electrical system. l

In the illustrative embodiment of the invention, the lifting mechanismis electrically operated and the truck is propelled manually.Previously, lifttrucks have been known where the lifting operation isperformed by a motor, but these trucks have been large and heavy. It hasbeen quite universal to propel these trucks by large motors, and, infact, the operator normally has ridden on the truck. This has resultedin the trucks being expensive to manufacture and operate so that the eldof use has been very limited. Furthermore, the size and weight of thesetrucks has seriously interfered with their use. For example, these heavytrucks cannot be manipulated and maneuvered in lsmall quarters, and theycannot be lifted on the usual elevators in buildings.

Small hand-operated trucks are common, but they have the objectionablecharacteristic that the operator must lift the load manually. This notonly limits the users of the truck to workmen who could perform thelifting operation, but at times it has been an actual source of danger.With some such prior trucks, where the lifting is performed by swingingthe steering handle, the workman was endangered by the flying handle;that is, when the truck was lifted by the steering handle, the latch wasapt to be accidentally released with the result that the steering handlewould be -suddenly thrown upwardly. Frequently this has been the causeof severe injury to workmen. In addition, manual lifting has resulted ininjury to the truck because the workman failed to realize the limitationof the truck. Vlor example, workmen have attached an extension to thesteering handle and then attempted to lift loads beyond the capacity ofthe manual lifting mechanism; the result may have been that the load waslifted but the truck parts were bent or broken. Accordingly, workmenmust be watched continuously when they are using certain of the priortypes of trucks. It is an object of this invention to overcome thesedicultfes and to provide a truck which is satisfactory in all respects.

The lift truck shown in the drawings is provided with a chassis formedby a lower supporting frame, supporting wheels, and a steering handle.The steering handle is pivoted at the front end of the truck so that itmay be swung from a Vertical to a horizontal position, and the frontwheels are turned by swinging the steering handle about a vertical axis.Mounted upon the chassis is a lifting frame which is moved to and from araised position where it engages and lifts the load. The lifting isperformed by a motor lift mechanism which is mounted upon the chassisadjacent the steering handle; thus, the operator may control the liftingoperation and observe the elevating of the load. In this embodiment, thelifting frame is held in the raised position by a mechanical latch andthe descent is controlled by an automatic checking mechanism.

The motor lift mechanism is an electric motor operating through a camassembly and having no direct mechanical connection with the liftingframe. The operation of the electric motor is automatically controlledso that the lifting mechanism is always returned to a predeterminedinitial position at the end of the lifting cycle. This predeterminedinitial position is such that, when the lifting cycle is started, themotor immediately starts to elevate the lifting frame. Thus, there is notime delay as might be present if the operation of the motor werecontrolled manually.

Referring particularly to Figures 1 and 3 of the drawings, thesupporting frame is formed by a pair of rails 6 and 1, secured by a tiebar 8, and attached at the forward end of the truck by a head I8.Pivotally mounted in the head I8 is a fork 9 (see also Figure 2),carrying the front wheels I and II. The rear portion of the truck is notshown in the drawings but is of the type shown in my prior United StatesPatent No. 2,280,104, issued April 21, 1942. The lifting frame is formedby two side rails I and 2 attached at their forward ends by a saddle 3and at the rear of the truck by frame members (not shown). The liftingframe is pivoted to the supporting frame by links 4 and 5 at the front,and by similar links at the rear.

The king bolt of fork 9 extends through head I8 and has rigidly attachedtoits upper end a collar I2. Pivoted to collar I2 is a steering handleI3 which is adapted to swing from the upright position shown in Figure lto a position for steering the truck, such as shown in Figure 4. Thesteering handle is balanced by a compression spring I4, coiled about aguide rod i between a bearing bracket I1 to which the guide rod ispivoted and a bracket IS upon the handle. The base of the handle carriesa stop I9 which engages a cooperating stop portion of collar I2 to holdthe handle in the position shown in Figure 1.

As indicated above, the elevating of the lifting frame is performed byan electric motor operating through suitable gearing, and controlled sothat when operated, a complete lifting cycle is carried on. The entireelevating mechanism is located between the forward end of the liftingframe and head I8. At the top (Fig. 2) a battery box ZI encloses abattery 52 and is supported on the top of a gear box 20. A motor 22 ismounted on the side of the gear box (see Figure 3, and carries a pinion82, meshing with a gear 83. Gear 83 in turn carries a pinion 84, whichmeshes with a gear 85 carrying a pinion 86. Pinion 86 drives a gear 81which has a pinion driving a gear (not shown) which drives a gear 88 ona shaft 24. Shaft 24 extends transversely of the truck and is rigidlysupported for rotation in bearings at the bottom of the gear box. Theends' of shaft 24 overhang, and rigidly mounted on these ends are crankarms 25 and Y26. Each of these crank arms carries at its extreme end alifting roller 89 (see also Figure 4). Mounted upon the lifting frame inalignment with these lifting rollers are lifting hooks 30 and 3|, whichare pivoted at their rear ends to saddle 3 of the lifting frame (Figures1 and 4) and which are provided at their forward ends with hook portions28 and 29, respectively. As will be explained below, the lifting frameis elevated by rotating arms 25 and 26 so that rollers 89 move under andengage hook portions 23 and 29, pulling the frame up.

Rigidly mounted on the frame at the side of lifting hook 39 is a guideplate 55, and extending from the hook over the top of the guide plate isa stop 92; similarly, (see Figure 3) lifting honk 3I is provided with aguide plate 56 and a stop 93. When engaged by rollers 89 on the arms,the

hooks are lifted from these plates, but when the arms move downwardly,the stops engage the plates, disengaging the hooks from the rollers; thehooks then rest on the guide plates until they are engaged again by thearms.

The lifting frame is held in its elevated position by treadle 44 (seeFigure 3) mounted on the side of gear box 20, and having a hook 45 whichengages a roller 46, mounted on saddle 3 of the lifting frame. Treadle44 has a foot extension 41, which is depressed to release the frame. A

spring 50, carried at its upper end by a pin on the gear box, biases theforward end of the treadle upwardly against the stop 5I which extendsfrom the gear box. A check 48 controls the descent of the lifting framebut does not interfere with the elevating operation.

The operation of the motor is controlled by mechanism shown at thecentral portion of Figure 4. At the top, a handle lever 32 is rockablymounted on a pivot 33, extending from the bottom of battery box 2I. Atthe right, the handle lever is provided with a cylindrical shell whichencloses a plunger 90. The stem of the plunger extends from the top ofthe shell and is held by a pair of lock nuts 9i, and within the shell aspring 34 biases the plunger downwardly. Directly beneath the plunger,and in operative relationship therewith, isa control switch 35, which ismounted on a bracket 36 on the bottom of the battery box. The handlelever is biased to the left by a spring 49, the right-hand end of whichis attached to the handle lever, and the left-hand Vend of which iscarried by a pin on the side of the battery box. When the handle leveris swung clockwise from the position shown in Figure 4 to the positionshown in Figure 1, the plunger engages and close switch 35, thusstarting the motor.

Extending downwardly from handle lever 32 is a latch finger 40. Pivotedon the gear box directly beneath the latch finger is a trip lever 31,which is formed by a downwardly extending release arm 39, a stop portion43 at the top and, at the left, a latch portion 38. A spring 4I, havingits left end fixed to the gear box and its right end attached to thetrip lever, biases the trip lever in a clockwise direction. When in theposition shown in Figure 4, stop portion 43 limits the counterclockwiseswinging movement of handle lever 32.

Lifting arm 26 has integral therewith an arcuate member 21 which rotatesin alignment with release arm 39. When the cam member 21 is opposite therelease arm 39, the release arm is engaged, and the trip lever is heldin the position shown in Figure 4 with spring 4I held under tension.However, when the cam member moves away from the release arm, the triplever tends to swing to the right due to the action of the spring towardthe position shown in Figure 1. Thus, when the handle lever is swung toclose switch 35, and the arcuate member 21 has moved away from releasearm 39, the latch portion 38 swings below the latch linger 40, therebylatching the lever handle in the position shown in Figure l with switch35 closed. Subsequentlycam member 21 engages release arm 39, swinginglatch lever 31 counterelockwise with the result that latch finger 48 isreleased. This permits spring 49 to swing handle lever 32counterclockwise with the result that switch 35 opens, stopping themotor.

The electric circuit for the motor is shown in Figure 5. The motor 22,one side of switch 35 and the negative side of battery 52 are allgrounded to the frame, and the other side of each is connected to arelay53. Relay 53 is of known construction and is such that when switch 35 isclosed', motor 22 is connected to the positive side of the battery `soVthat the motor starts; and when switch`35 is lreopened, the motorisstopped.

When a load is to be lifted, the handle lever 32 `is swung from theposition shown in Figure 4 to the positionwshown in Figure 1, therebyclosing switch 35. The motor immediately starts with the result thatarms 25 and 26 are rotated. R'eferring specifically to Figure 1, rollers89 engage hooks 28 and 29, and the lifting frame is pulled bythe hooksinto the elevated position shown in AFigure 4. At this time roller 4Band hook 45 of treadle 44 become engaged, holding the lifting frame inthe elevated position. However, during this initial movement, cam member21 engages release arm 39 and holds latch lever 31 in the position ofFigure 4. Thus, at any time during this initial movement, if theoperator so desires, he can release the handle lever and the motor isimmediately disconnected; -the load will then recede of its own weight.`However, at the time hook 45 engages roller 46, cam Vportion 21 movesfrom engagement with release arm 39 with the result that the handlelever is latched in the position shown in Figure 1, and the releasing ofthe handle lever will not result in stopping the motor. The motorcontinues to run, and arms 25 and 25 carry hooks 30 and 3l down so thatstops 92 and 93 engage plates 55 and 56, and the arms move away from thehooks, When arms 25 and 26 reach the position shown in Figure 1, releasearm 39 is engaged by cam portion 21, and further movement of the camportion releases handle lever 32 and stops the motor. However, the motorcoasts so that at the time it stops, arms 25 and 25 are so positioned(as shown in Figure 4) that upon the restarting of the motor, rollers 89on the arms will immediately engage their lifting hooks.

When it is desirable to lower the load, foot portion 41 of treadle 44 isdepressed, releasing the engagement between hook 45 and roller 45 andpermitting the load to descend under the control of check 48. When thetruck is descending, hook stops 92 and 93 ride along the tops of guideplates 55 and 56, thus, positioning the hooks to be engaged for liftingthe lifting frame again.

As many possible embodiments may ibe made of the above invention and asmany changes might be made in the embodiment above set forth, it is tobe understood that all matter hereinbefore set forth, or shown in theaccompanying drawings, is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. In a lift truck construction, the combination of: a chassiscomprising a supporting frame, a plurality of wheels supporting saidframe, and a steering handle; load engaging means mounted on said frameand adapted to be moved from a lowered position to a position in whichit engages and lifts the load; and elevating means to elevate said loadengaging means comprising a motor mounted on said frame and havingassociated therewith means constituting a source of electric power and aswitch to be closed to operate the motor, a lifting arm assemblyrotatably mounted and connected to said motor to be rotated upon theoperation of said motor, cooperating means mounted on said load engagingmeans in alignment with said lifting arm assembly and adapted to beengaged by said lifting arm assembly upon the rotation thereof by saidmotor with the result that said lifting arm assembly elevates said loadengagingmeans, and latch means to hold the switch closed after the loadhas been elevated and until the lifting arm assembly has been moved to"a predetermined initial position.

` 2. In a lift truck constructionin which a lift- Ationftorotate saidcam means one complete revolution from a predetermined initial position,and cooperating means mounted on said lifting frame -to be engaged byvsaid cam means duringthe initialportion of the rotary movement of saidcam means whereby said cam means elevates said lifting frame andthereafter ccntinues'to move from engagement with said cooperatingmeans. 3. In a lift truck constructionin which a lifting frameis mountedon achassis to be moved to and from an elevated position wherein itengages ancl lifts a load, a'pair of lifting arms rotatably mounted onsaid chassis at the opposite sides thereof, motive means geared to saidlifting arms and adapted upon energization to rotate said liftingarmsone complete revolution from a predetermined initial position, apairof hooksl pivotally mounted on said' lifting frame to be engaged bysaid lifting arms during the initial portion Aof the rotary movement ofsaid lifting .arms whereby said cam means elevates said lifting frameand thereafter continues to move from engagement with said hooks, a pairof guide plates mounted respectively at the sides of said hooks, andstop means on each of said hooks extending over the top of the adjacentguide plate, whereby said stops hold said hooks from falling below asubstantially horizontal position.

4, In a lift truck construction in which a lifting frame is mounted on achassis to be moved to and from an elevated position wherein it engagesand lifts a load, a gear casing mounted on said chassis between thefront end of the chassis and the front end of the frame, cam meansrotatably mounted on said casing, motive means mounted on said casingand geared to said cam means and adapted upon energization to rotatesaid cam means one complete revolution from a predetermined initialposition, and cooperating hook means mounted on said lifting frame to beengaged by said cam means during the initial portion of the rotarymovement of said cam means whereby said cam means elevates said `liftingframe and thereafter continues to move from engagement with saidcooperating means.

5. In a lift truck construction in which a lifting frame is mounted on achassis so as to be raised from a lowered. position to an elevatedposition wherein it engages and lifts the load, means for automaticallyraising the lifting frame comprising, link means pivotally attached tothe lifting frame and having engaging means eX- tending forwardly withrespect to the lifting frame, crank arm means rotatably mounted andadapted to engage said engaging means and to exert a lifting force whichis eective to raise the lifting frame, a motor geared to said crank armmeans to rotate said crank arm means, a control switch which is closedto operate said motor thereby to elevate the lifting frame, an armadapted to beA moved manually to close said switch, a spring actuateddog to engage said arm and hold said switch closed, and means mounted to`rotate with said crank arm to engage said `dog iand release said 'armto stop the `motor after lifting frame is swingably mounted on aVchassis whereby the lifting frame swings from a lower position to anelevated position upon a plurality of similar links one end of each ofwhich is pivoted to the chassis and the other end of each of which ispivoted to the lifting frame and wherein the lifting frame is held inthe elevated position by a releasable latch means, means to elevate vthelifting frame comprising, a pair of elongated hook links mounted uponthe opposite sides of the Ilifting frame each of said hook links beingattached at one end to the lifting frame and having at its other end ahook portion which is open downwardly, a gear casing positioned betweensaid hook portions and mounted on said chassis, a pair of crank armsassociated respectively with the two hook links, a crank shaft rotatablymounted on said gear casing and having said crank arms rigidly mountedon its ends, a motor mounted on said gear casing and geared to saidcrank shaft through a speed reduction gear 'train in said gear casing,and motor control means to operate said motor thereby to cause the crankarms to engage the hook links and elevate the lifting frame.

7. In a lift truck construction, the combina'- tion of: a vchassis`comprising 'a supporting frame, a plurality `of wheels supporting saidframe, and a steering handle; loadengaging means mounted on said frameand adaptedto be moved from a lowered position to a position in which itengages and lifts the load; and elevating means to elevate said loadengaging means comprising, a motor mounted on said frame and havingassociated therewith means constituting a source Vof lelectric power'and control means to operate the motor including a lever Which is movedVfrom an off position to an on position to -start the motor., a liftingarm assembly rotatably mounted and connected to said motor to be rotatedupon the operation of said motor, and cooperating means mounted on saidload engaging means in alignment with said lifting arm assembly andadapted to be engaged by said lifting arm assembly upon the rotationthereof by said motor with the result that said lifting arm assemblyelevates said load engaging means, said lifting arm as- -semblyincluding a cam vwhich is effective to cause said lever to be moved fromits on position tov 'its 01T position when the liftingarm assembly hascompleted one revolution with the result that the motor is automaticallystopped.

WnJLiAM sTUEBINQ-JR.

